Absorption Coefficient of Phytoplankton at 443nm (aph in m^-1 at 4km resolution): The absorption coefficient aph represents the fraction of incident light absorbed by phytoplankton organisms. It is an index of variability of the phytoplankton biomass in marine and coastal turbid waters.

General information: Monthly anomalies absorption coefficient due to phytoplankton at 443nm in m^-1 derived from the MODIS-AQUA sensor. Processing information: aph(443) data is processed using SeaDAS 6.4 software and the QAA algorithm (Lee et al., 2002). Temporal characteristics: This dataset consists of standard mapped image Monthly anomalies sea surface layer aph(443) maps at 9km resolution (L3 product). Description of observation methods/instruments: The remote sensing of 'Ocean Colour' represents a measure of the spectral variations in the light leaving the water surface, subsequently interpreted in terms of concentrations of optically-significant constituents in the water. The electromagnetic signal collected by the sensor on-board the satellite is largely determined by photons that have never reached the water surface, but have been backscattered within the atmosphere through multiple interactions between gas molecules and aerosols. After removing the atmospheric contribution, the water leaving radiance recorded at a given time by the satellite reflects the optical properties of the water which, in turn, mirrors a specific structure and biogeochemical composition of the marine waters. The satellite-derived reflectance at the air-sea interface is related to inherent optical properties of the water constituents including aph(443). Quality/accuracy/calibration information: The calculation is based on a semi-analytical bio-optical algorithm. More details as well as validation results are given in Lee et al. (2002), IOCCG (2006) or Melin et al. (2007). References: Lee, Z.-P., Carder, K.L., Arnone, R.: Deriving inherent optical properties from water color: A multiband quasi-analytical algorithm for optically deep waters. Appl. Opt., 41, 5755-5772, 2002. IOOCG Report 5: Remote sensing of inherent optical properties: Fundamentals, tests of algorithms, and applications, Eds. Z.-P. Lee, 126pp., 2006. Mélin,F., Zibordi, G., Berthon, J.-F.: Assessment of satellite ocean color products at a coastal site. Remote Sens. Environ., 110, 192-215, 2007. Other contextual information: The product is stored in NetCDF data confirming to the COARDS-CF conventions and delivered through FTP, OpenDAP and Live Access Server (work in progress). Other contextual information: The product is stored in NetCDF data and available for download.

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